Cytotoxicity Of Carbon Nanotubes Research Articles

Self-assembled electrochemically active biofilms doped with carbon nanotubes: Electron exchange efficiency and cytotoxicity evaluation

Thick electrochemically active biofilms (EABs) will lead to insufficient extracellular electron transfer (EET) rate because of the limitation of both substrate diffusion and electron exchange. Herein, carbon nanotubes (CNTs)-doped EABs are developed through self-assembly. The highly conductive biofilms (internal resistance of ∼211 Ω) are efficiently enriched at CNTs dosage of 1 g L−1, with the stable power output of 0.568 W m−2 over three months. The embedded CNTs can act as electron tunnel to accelerate the EET rate in thick biofilm. Self-charging/discharging experiments and Nernst-Monod model stimulation demonstrate a higher net charge storage capacity (0.15 C m−2) and more negative half-saturation potential (−0.401 V) for the hybrid biofilms than that of the control (0.09 C m−2, and −0.378 V). Enzyme activity tests and the observation of confocal laser scanning microscopy by live/dead staining show a nearly negligible cytotoxicity of CNTs, and non-targeted metabonomics analysis reveals fourteen differential metabolites that do not play key roles in microbial central metabolic pathways according to KEGG compound database. The abundance of typical exoelectrogens Geobacter sp. is 2-fold of the control, resulting in a better bioelectrocatalytic activity. These finding provide a possible approach to prolong electron exchange and power output by developing a hybrid EABs doped with conductive material.

Cytotoxicity of Carbon Nanotubes, Graphene, Fullerenes, and Dots.

The cytotoxicity of carbon nanomaterials is a very important issue for microorganisms, animals, and humans. Here, we discuss the issues of cytotoxicity of carbon nanomaterials, carbon nanotubes, graphene, fullerene, and dots. Cytotoxicity issues, such as cell viability and drug release, are considered. The main part of the review is dedicated to important cell viability issues. They are presented for A549 human melanoma, E. coli, osteosarcoma, U2-OS, SAOS-2, MG63, U87, and U118 cell lines. Then, important drug release issues are discussed. Bioimaging results are shown here to illustrate the use of carbon derivatives as markers in any type of imaging used in vivo/in vitro. Finally, perspectives of the field are presented. The important issue is single-cell viability. It can allow a correlation of the functionality of organelles of single cells with the development of cancer. Such organelles are mitochondria, nuclei, vacuoles, and reticulum. It allows for finding biochemical evidence of cancer prevention in single cells. The development of investigation methods for single-cell level detection of viability stimulates the cytotoxicity investigative field. The development of single-cell microscopy is needed to improve the resolution and accuracy of investigations. The importance of cytotoxicity is drug release. It is important to control the amount of drug that is released. This is performed with pH, temperature, and electric stimulation. Further development of drug loading and bioimaging is important to decrease the cytotoxicity of carbon nanomaterials. We hope that this review is useful for researchers from all disciplines across the world.

The Cytotoxicity of Carbon Nanotubes and Hydroxyapatite, and Graphene and Hydroxyapatite Nanocomposites against Breast Cancer Cells.

Cancer is a current dreadful disease and the leading cause of death. Next to cardiovascular diseases, cancer is the most severe threat to human life and health. Breast cancer is the most common invasive cancer diagnosed in women. Each year about 2.3 million women are diagnosed with breast cancer. In consideration of the severity of breast cancer, herein we designed the biocompatible nanomaterials, CNTs-HAP and GR-HAP, through grafting of hydroxyapatite (HAP) to carbon nanotubes (CNTs) and graphene (GR) nanosheets. CNTs-HAP and GR-HAP have been tested for their cytotoxicity, growth and motility inhibitory effects, and their effects on the mesenchymal markers. All these demonstrated significant dose-dependent and time-dependent in vitro cytotoxicity against SUM-159 and MCF-7 breast cancer cell lines. The cell viability assay showed that the CNTs-HAP was more effective over SUM-159 cells than MCF-7 cells. It found that the increase in the concentration of GR-HAP has inhibited the clonogenic ability of breast cancer cells. The GR-HAP exhibited a substantial inhibitory effect on the cell motility of SUM-159 cell lines. It was investigated that the expression of vimentin (mesenchymal marker) was majorly reduced in SUM-159 cells by GR-HAP.

Slime molds response to carbon nanotubes exposure: from internalization to behavior

Carbon nanotubes (CNTs) offer attractive opportunities due to their physical, electrical, mechanical, optical, and thermal properties. They are used in a wide range of applications and are found in numerous consumer products. On the downside, their increasing presence in the environment poses potential threats to living organisms and ecosystems. The aim of this study was to evaluate the toxicity of double-walled carbon nanotubes (DWCNTs) on a new model system: the acellular slime mold Physarum polycephalum. Despite its ecological significance, its simplicity of organization, and its behavioral complexity, exposure of such organisms to nanoparticles has been poorly investigated. Slime molds were exposed to DWCNTs using three routes of exposure (topical, food, environment). We first demonstrated that DWCNTs were rapidly internalized by slime molds especially when DWCNTs were mixed with the food or spread out in the environment. Secondly, we showed that a 6-week exposure to DWCNTs did not lead to bioaccumulation nor did it lead to persistence in the slime molds when they entered a resting stage. Thirdly, we revealed that 2 days following exposure, DWCNTs were almost entirely excreted from the slime molds. Lastly, we uncovered that DWCNTs exposure altered the migration speed, the pseudopods formation, and the expansion rate of the slime molds. Our results extend our current knowledge of CNTs cytotoxicity and introduce P. polycephalum as an ideal organism for nanotoxicology.

The Interplay between Whey Protein Fibrils with Carbon Nanotubes or Carbon Nano-Onions.

Whey protein isolate (WPI) fibrils were prepared using an acid hydrolysis induction process. Carbon nanotubes (CNTs) and carbon nano-onions (CNOs) were made via the catalytic chemical vapor deposition (CVD) of methane. WPI fibril–CNTs and WPI fibril–CNOs were prepared via hydrothermal synthesis at 80 °C. The composites were characterized by SEM, TEM, FTIR, XRD, Raman, and TG analyses. The interplay between WPI fibrils and CNTs and CNOs were studied. The WPI fibrils with CNTs and CNOs formed uniform gels and films. CNTs and CNOs were highly dispersed in the gels. Hydrogels of WPI fibrils with CNTs (or CNOs) could be new materials with applications in medicine or other fields. The CNTs and CNOs shortened the WPI fibrils, which might have important research value for curing fibrosis diseases such as Parkinson’s and Alzheimer’s diseases. The FTIR revealed that CNTs and CNOs both had interactions with WPI fibrils. The XRD analysis suggested that most of the CNTs were wrapped in WPI fibrils, while CNOs were partially wrapped. This helped to increase the biocompatibility and reduce the cytotoxicity of CNTs and CNOs. HR-TEM and Raman spectroscopy studies showed that the graphitization level of CNTs was higher than for CNOs. After hybridization with WPI fibrils, more defects were created in CNTs, but some original defects were dismissed in CNOs. The TG results indicated that a new phase of WPI fibril–CNTs or CNOs was formed.

Formation of a bovine serum albumin diligand complex with rutin and single-walled carbon nanotubes for the reduction of cytotoxicity

Carbon nanotubes (CNTs) are extensively used in the area of biotechnology and biomedicine, and the binding of proteins to CNTs plays an important role in the potential toxicity of nanomaterials. Rutin is a glycoside of the bioactive quercetin with various health-improving effects due to its antioxidant ability. Demonstration of the interaction between serum albumin and bioactive components is important to design effective carriers for the suppression of CNTs’ toxicity. In this study, bindings of bovine serum albumin (BSA) to single-walled CNTs and/or rutin were investigated by fluorescence and molecular docking techniques. The fluorescence of BSA was significantly quenched by both CNTs and rutin in static mode, which was confirmed by the Stern-Volmer calculations. Although rutin showed higher affinity to protein than CNTs, the interactions of both components with BSA did mainly locate within subdomain IIA (site I). BSA-diligand complexes were successfully formed after the simultaneous addition of CNTs and rutin. Bioactive rutin in the BSA-diligand complex still kept strong free radical scavenging activity compared to free rutin or BSA-monoligand complex. Consistently, the cytotoxicity of CNTs and reactive oxygen species formation in endothelial cells was reduced in the BSA-diligand complexes relative to those of BSA-CNTs corona or CNTs alone, where the co-presence of rutin played an important role. These findings suggest the possibility and advantage of designing BSA-based carriers for the suppression of CNTs’ toxicity in their biomedical applications.

Molecular dynamics simulations of adsorption of long pyrene-PEG chains on athin carbon nanotube

Carbon nanotubes have emerged as highly promising theranostic agents due to their unique structural/physical features, high surface area, and high drug-loading capacity. The high cytotoxicity of carbon nanotubes can be eliminated by noncovalent coating using hydrophilic polymers. We investigated the adsorption of long pyrene functionalized polyethylene glycol (PEG) chains, PEG$_{2000}$ and PEG$_{5000}$, on a single-walled carbon nanotube (SWNT) from a crowded solution. Full-atom molecular dynamics simulations in explicit water were used to mimic the experimental conditions of noncovalent PEGylation with a stoichiometry of one SWNT to ten pyrene-PEG. Although the diffusional behavior of the pyrene molecules still attached to the polymers did not change according to chain length, the adsorption rate for pyrene-PEG$_{2000}$ to the SWNT was higher than that for pyrene-PEG$_{5000}$ chains. Here longer chains sterically hindered the adsorption of pyrene groups on the SWNT surface. Once adsorbed, pyrene molecules stayed on the SWNT surface even though they frequently adopted different orientations that may weaken their $\pi -\pi $ stacking interactions with the nanotube surface.

Consequences of Hydrophobic Nanotube Binding on the Functional Dynamics of Signaling Protein Calmodulin.

The wide applications of nanomaterials in industry and our daily life have raised growing concerns on their toxicity to human body. Increasing evidence links the cytotoxicity of nanoparticles to the disruption of cellular signaling pathways. Here, we report a computational study on the mechanisms of the cytotoxicity of carbon nanotubes (CNTs) by investigating the direct impacts of CNTs on the functional motions of calmodulin (CaM), which is one of the most important signaling proteins in a cell, and its signaling function relies on the Ca2+ binding-coupled conformational switching. Computational simulations with a coarse-grained model showed that binding of CNTs modifies the conformational equilibrium of CaM and induces the closed-to-open conformational transition, leading to the loss of its Ca2+-sensing ability. In addition, the binding of CNTs drastically increases the calcium affinity of CaM, which may disrupt the Ca2+ homeostasis in a cell. These results suggest that the binding of hydrophobic nanotubes not only inhibits the signaling function of CaM as a calcium sensor but also renders CaM to toxic species through sequestering Ca2+ from other competing calcium-binding proteins, suggesting a new physical mechanism of the cytotoxicity of nanoparticles.

Time-dependent degradation of carbon nanotubes correlates with decreased reactive oxygen species generation in macrophages.

Introduction and objective: With the increase in carbon nanotube-based products on the commercial market, public concern regarding the possible toxicity of these nanomaterials has attracted much attention. Although previous studies found no obvious toxicity related to carbon nanotubes (CNTs), their safety has not been established because long-term evaluation is still needed. In vitro assays are used to understand the toxicity of nanomaterials. However, the data published so far were generated in short-term assays in which cells are continuously exposed to CNTs. Therefore, the objective of this study is to quantitatively assess the relative long-term cytotoxicity and degradation of CNTs after uptake by macrophages.Methods: We used macrophage cell line of RAW 264.7 and primary rat Kupffer cells to investigate macrophage uptake of CNTs as well as their quantity changes up to a relatively late time point after uptake (7 days) by measuring optical absorbance in the near infrared region and Raman spectra of CNTs in the cell lysates. The time-dependent cytotoxicity was evaluated by measuring reactive oxygen species (ROS), glutathione, cell viability, and caspase 3/7 activity in 1–7 days.Results: CNTs were degraded by approximately 25–30% within first 4 days after uptake; however, and no additional degradation occurred for the remainder of the 7-day test period. Generation of ROS by macrophages decreased as CNT degradation occurred, returning to control levels by Day 7. In the meantime, the glutathione level gradually recovered over time. There were no changes in cell viability or caspase 3/7 activation during CNT degradation.Conclusion: These results confirm that degradation of CNTs by macrophages is associated with ROS generation. The data also suggest that CNT cytotoxicity decreases as they are degraded.

Do carbon nanotubes inhibit or promote amyloid fibrils formation?

Objectives: The purpose of the work was to study the effect of carbon nanotubes on the formation of fibril structures in lysozyme at room temperature under different pH values. Materials and methods: For the preparation of the samples, hen egg-white lysozyme protein (HEWL, Fluka), as well as single-walled (SWCNT, Sigma-Aldrich) and multi-walled (MWCNT, OOO TM “Spetsmash”, Kyiv, Ukraine) carbon nanotubes were used. Used techniques: IR-Fourier Absorption Spectroscopy; confocal microscopy. Results: In this paper, the study of molecular mechanisms of interaction of lysozyme with carbon nanotubes by vibrational spectroscopy was carried out and a conformational analysis of the formed complexes was performed. It is shown that carbon nanotubes can affect the structure of lysozyme even at room temperature and normal pH values, as evidenced by conformational changes in lysozyme due to interaction with carbon nanotubes. Complexes which are formed as a result of such interaction, have characteristic features of amyloid fibrillar structures. It reveals one of possible mechanisms of carbon nanotubes cytotoxicity. On the other hand, such a technique can be introduced to obtain model amyloid fibrils for further study. Conclusion: The method of vibtarional spectroscopy has shown that carbon nanotubes can influence the structure of lysozyme, as it is shown by the conformational analysis of the absorption band Amide I. After the interaction of lysozyme with CNT, an increase in the contribution of antiparallel β-conformation in the structure of lysozyme is observed, and the contribution of the α-helix conformation is reduced, which are characteristic features in the formation of fibrillar structures. The possibility of amyloid fibril formation without the use of high temperatures at different pH values with the interaction of lysozyme and carbon nanotubes, which can be applied as a method for obtaining the model amyloid fibrils, is shown.

Adsorption of Plasma Proteins on Single-Walled Carbon Nanotubes Reduced Cytotoxicity and Modulated Neutrophil Activation.

Proteins in the bloodstream bind to carbon nanotubes (CNTs) through noncovalent interactions to form a protein corona, thereby effectively influencing the biological properties and blood biocompatibility of the CNTs. Here, we investigated the binding of common plasma proteins (i.e., human immunoglobulin G (IgG), human serum albumin (HSA), and fibrinogen (FG)) to carboxylated single-walled CNTs (SWCNTs), and evaluated the effects of these different protein coronas on cytotoxicity to endothelial cells and immune response to neutrophils in the bloodstream. Measurements of adsorption parameters revealed tight binding of proteins to SWCNTs, and the SWCNTs adsorption capacities followed the order FG > HSA > IgG. In addition, the basic residues (Arg, Lys, His) were found to play an important role in the formation of protein-SWCNTs corona complexes and determine their adsorption capacity. Consistent with the higher protein adsorption capacity, FG more significantly reduced the cytotoxicity of CNTs to human umbilical vein endothelial cells than the other two proteins. However, only treatment of SWCNTs with IgG resulted in the enhancement of CNT-induced myeloperoxidase (MPO) release (i.e., neutrophil activation) in neutrophils, while MPO-dependent degradation of CNTs induced less cytotoxicity than initial nanomaterials. Consistent with these effects of protein coronas, the presence of serum attenuated the cytotoxicity of CNTs and CNTs could induce neutrophil activation in human blood plasma. Our study demonstrates the ability of adsorbed plasma proteins to influence cytotoxicity and neutrophil response caused by CNTs in the bloodstream.

Attenuation of bacterial cytotoxicity of carbon nanotubes by riverine suspended solids in water.

The impact of solid particles on ecotoxicity of nanomaterials in water environments is poorly understood. This study investigated the effect of natural riverine suspended solids (SPS) on the cytotoxicity of single-walled carbon nanotubes (SWCNTs) towards a bacterium, Ochrobactrum sp. in water. Compared with SWCNT suspension without SPS, the presence of SPS at different concentrations ranging from 20 to 400mgL-1 markedly increased the survival rates of bacteria exposed to 50mgL-1 SWCNTs and bacterial survival rates increased with SPS concentrations by a power law. Sedimentation experiments and field emission scanning electron microscopy revealed the occurrence of heteroaggregation between SWCNTs and SPS, probably responsible for the reduced SWCNT toxicity. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (ExDLVO) calculation showed the mitigated toxicity might also result from the decreased SWCNT-bacterium interaction energy with the increased SPS concentrations and the stronger SPS-SWCNT interaction than the SWCNT-bacterium interaction. This work provides new insights into our understanding of environmental hazards of engineered nanomaterials in aquatic systems.

Influence of CNTRENE® C100LM carbon nanotube material on the growth and regulation of Escherichia coli.

The growing use of carbon nanotubes (CNTs) in industrial and consumer products raises important questions about their environmental fate and impact on prokaryotes. In the environment, CNTs are exposed to a variety of conditions (e.g., UV light) that could lead to decomposition and changes in their chemical properties. Therefore, the potential cytotoxic effect of both pristine and artificially aged carboxyl functionalized CNTRENE® C100LM CNTmaterial at neutral and acidic conditions on Escherichia coli K12 was analyzed using a minimal inhibitory concentration (MIC) assay, which also allowed monitoring of non-lethal growth effects. However, there were no observable MIC or significant changes in growth behavior in E. coli K12 when exposed to pristine or aged CNTs. Exposure to pristine CNTRENE® C100LM CNT material did not appear to influence cell morphology or damage the cells when examined by electron microscopy. In addition, RNA sequencing revealed no observable regulatory changes in typical stress response pathways. This is surprising considering that previous studies have claimed high cytotoxicity of CNTs, including carboxyl functionalized single-walled CNTs, and suggest that other factors such as trace heavy metals or other impurities are likely responsible for many of the previously reported cytotoxicity in E. coli and possibly other microorganisms.

Carbon nanotubes gathered onto silica particles lose their biomimetic properties with the cytoskeleton becoming biocompatible.

Carbon nanotubes (CNTs) are likely to transform the therapeutic and diagnostic fields in biomedicine during the coming years. However, the fragmented vision of their side effects and toxicity in humans has proscribed their use as nanomedicines. Most studies agree that biocompatibility depends on the state of aggregation/dispersion of CNTs under physiological conditions, but conclusions are confusing so far. This study designs an experimental setup to investigate the cytotoxic effect of individualized multiwalled CNTs compared to that of identical nanotubes assembled on submicrometric structures. Our results demonstrate how CNT cytotoxicity is directly dependent on the nanotube dispersion at a given dosage. When CNTs are gathered onto silica templates, they do not interfere with cell proliferation or survival becoming highly compatible. These results support the hypothesis that CNT cytotoxicity is due to the biomimetics of these nanomaterials with the intracellular nanofilaments. These findings provide major clues for the development of innocuous CNT-containing nanodevices and nanomedicines.

Obtaining a full range of surface energies on single wall carbon nanotube samples through photo-initiated chemical vapor deposition

Event Abstract Back to Event Obtaining a full range of surface energies on single wall carbon nanotube samples through photo-initiated chemical vapor deposition Seyedehsan Hosseininasab1, Nathalie Faucheux2, Gervais Soucy2 and Jason R. Tavares1 1 Polytechnique Montreal, Chemical engineering, Canada 2 Université de Sherbrooke, Chemical and Biotechnological Engineering, Canada Introduction: Despite all the distinctive properties of carbon nanotubes (CNTs), their commercial use in biomedical applications is limited by their cytotoxicity [1]. Several factors can explain the CNT cytotoxicity including their dimension, surface hydrophobicity and degree of agglomeration [1],[2]. However, the effect of surface energy on the cytotoxicity of single wall carbon nanotubes (SWCNTs) has to be investigated further. For this purpose, well-characterized SWCNTs bearing similar functionalities with properties ranging from super-hydrophobic to super-hydrophilic must be prepared. In this study, photo-initiated chemical vapor deposition (PICVD) using a syngas precursor [3] was applied to SWCNTs and is presented as a viable technique to fulfill this goal. Materials and Methods: Raw-SWCNTs (R-SWCNTs) were first purified by a multi-step protocol as previously described [4]. Efficiency of purification was assessed by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). These purified SWCNTs (P-SWCNT) were then dispersed in ethanol via sonication and immediately filtered under vacuum upon a polycarbonate membrane. The resulting “buckypaper” was placed in a vacuum oven to ensure complete ethanol evaporation. The surface of SWCNTs was then treated according to a method developed by Dorval Dion et al (2014) [3]. Briefly, P-SWCNTs were placed inside a UVC-illuminated quartz micro-reactor. After inert gas purging, the syngas precursor (CO and H2) was introduced at various ratios along with H2O2 as a radical photo-initiator (PI). To obtain the desired surface functionality, the process could be implemented under pressure (+15 kPag) or slight vacuum (-15 kPag). Hydrophilic surfaces were typically obtained under slight vacuum, while hydrophobic surfaces were achieved under pressure [3]. The surface energy of the treated P-SWCNTs was determined by applying the Owens-Wendt model [5]. Results and Discussion: TEM was used to both confirm the efficiency of the purification protocol and assess the morphology of P-SWCNTs after treatment. As shown Fig. 1A, the impurities in R-SWCNTs included amorphous and graphitic carbon, as well as catalytic metal nanoparticles, while these impurities in P-SWCNTs were decreased (Fig. 1B) (from 29% to 14% based on TGA results). Surface wetting of SWCNT samples was assessed through sessile drop contact angle measurements. The average contact angle of P-SWCNT samples was 79±2°, while it varied from 0+3° to 165±3° for treated nanotubes (T-SWCNTs) as a function of the molar ratio of H2/CO (Fig. 2). Conclusion: Using PICVD with a syngas precursor, we successfully functionalized P-SWCNTs bearing various oxygen-containing groups with properties ranging from superhydrophilic to superhydrophobic. This PICVD method will be helpful to better determine the effect of surface energy on the cytotoxicity of SWCNTs bearing similar functionalities. Fig. 1. TEM images of A) R-SWCNTs, B) P-SWCNTs. Fig. 2. Blue lozenge) Contact angle measurements of T-SWCNTs obtained by tensiometry in terms of molar ratio of H2/CO, Red Square) Surface energy measurements that have been plotted in terms of molar ratio. This project is supported by FRQNT Foundation

Conscious Changes of Carbon Nanotubes Cytotoxicity by Manipulation with Selected Nanofactors

We discuss eight major challenges in the field of carbon nanomaterial toxicity. Generally, we pick up some of them, and the most important challenge is searching of the qualitative relationships between nanofactors and cytotoxicity. This is important since it can provide the possibility of conscious changes of carbon nanotubes cytotoxicity by manipulation with selected nanofactors. Therefore, the toxicity of a series of gradually oxidized carbon nanotubes is studied. We show, for the first time, that toxicity of those materials depends strongly on the ratio of acidic to basic group concentration—the higher is this ratio value, the more toxic are nanotubes. In this way, by changing this ratio, one can change toxicity. This correlation is more evident after ultrasonication, and it is connected with the accessibility of charged groups for interactions with proteins. Toxicity also depends on the ability of nanotubes for protein adsorption. We suggest that the changes in the protein composition of medium, especially lack of important growth factors, inhibit cell proliferation.Electronic supplementary materialThe online version of this article (doi:10.1007/s12010-015-1607-1) contains supplementary material, which is available to authorized users.

Enhanced reduction of single-wall carbon nanotube cytotoxicity in vitro: Applying a novel method of arginine functionalization.

Biomedical applications of carbon nanotubes (CNTs) have attracted a lot of attention in recent years. However, the applications of CNTs in these fields of research are challenged by some properties such as their insolubility and cytotoxicity. To improve their solubility in physiological solutions or to reduce cytotoxicity, a variety of engineered biologically active molecules through functionalization processes are being designed. Application of appropriate biomolecules has become an interesting research area these days from both fundamental and application standpoints. In the present report, arginine amino acids were used for single-wall carbon nanotubes (SWCNTs) functionalization because of their bulky and polar side chain. The efficiency of SWCNTs conjugation with arginine was demonstrated by Fourier transform infrared and Raman spectroscopies and Sakaguchi assay. Cytotoxicity of functionalized CNTs was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on three different cell lines. Results indicated that functionalization of SWCNTs with arginine reduced their cytotoxicity extremely and hence make them more appropriate for biomedical applications. Moreover, it was concluded that sensitivity to CNT cytotoxicity depends on the type of tissue and cell line. Here, an impressive and novel method for biological functionalization of CNTs has been introduced.

Influence of different types of carbon nanotubes on muscle cell response.

The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs), before and after chemical surface functionalization on muscle cell response in vitro and in vivo conditions. Prior to biological tests the surface physicochemical properties of the carbon nanotubes (CNTs) deposited on a polymer membrane were investigated. To 'evaluate microstructure and structure of CNTs scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FTIR) were used. During in vitro study CNTs deposited on polymer membrane were contacted directly with myoblast cells, and after 7 days of culture cytotoxicity of samples was analyzed. Moreover, cell morphology in contact with CNTs was observed using SEM and fluorescence microscopy. The cytotoxicity of CNTs modified in a different way was comparable and significantly lower in comparison with pure polymer membrane. Microscopy analysis of cultured myoblasts confirms intense cell proliferation of all investigated samples with CNTs while for two kinds of CNTs myoblasts' differentiation into myotubes was observed. Histochemical reactions for the activity of enzymes such as acid phosphatase, cytochrome C oxidase, and non-specific esterase allowed the analysis of the extent of inflammation, degree of regeneration process of the muscle fibers resulting from the presence of the satellite cells and the neuromuscular junction on muscle fibers in contact with CNTs after implantation of CNTs into gluteal muscle of rat.

Cytotoxicity of carbon nanotube variants: A comparative in vitro exposure study with A549 epithelial and J774 macrophage cells

While production of engineered carbon nanotubes (CNTs) has escalated in recent years, knowledge of risk associated with exposure to these materials remains unclear. We report on the cytotoxicity of four CNT variants in human lung epithelial cells (A549) and murine macrophages (J774). Morphology, metal content, aggregation/agglomeration state, pore volume, surface area and modifications were determined for the pristine and oxidized single-walled (SW) and multi-walled (MW) CNTs. Cytotoxicity was evaluated by cellular ATP content, BrdU incorporation, lactate dehydrogenase (LDH) release, and CellTiter-Blue (CTB) reduction assays. All CNTs were more cytotoxic than respirable TiO2 and SiO2 reference particles. Oxidation of CNTs removed most metallic impurities but introduced surface polar functionalities. Although slopes of fold changes for cytotoxicity endpoints were steeper with J774 compared to A549 cells, CNT cytotoxicity ranking in both cell types was assay-dependent. Based on CTB reduction and BrdU incorporation, the cytotoxicity of the polar oxidized CNTs was higher compared to the pristine CNTs. In contrast, pristine CNTs were more cytotoxic than oxidized CNTs when assessed for cellular ATP and LDH. Correlation analyses between CNTs’ physico–chemical properties and average relative potency revealed the impact of metal content and surface area on the potency values estimated using ATP and LDH assays, while surface polarity affected the potency values estimated from CTB and BrdU assays. We show that in order to reliably estimate the risk posed by these materials, in vitro toxicity assessment of CNTs should be conducted with well characterized materials, in multiple cellular models using several cytotoxicity assays that report on distinct cellular processes.

The evaluation of toxicity of carbon nanotubes on the human adipose-derived-stem cells in-vitro.

Background:Carbon nanotubes (CNTs) have a large variety of applications in tissue engineering and biomedical devices. The biocompatibility and cytotoxicity of CNTs have been studied widely, however, up until now; there was uncertainty on how nanosized materials behave in the human body and stem cells. The current study describes the functionalized carbon nanotubes on adipose-derived stem cells (ADSCs) for viability and proliferation purposes in vitro.Materials and Methods:After chemical modification of the CNTs, the ADSCs were cultured in Dulbecco's Modified Eagle's. Medium (DMEM) having doses of 0.1, 1, 10, 20, 50, and 100 μg/ml of CNTs. On the third and seventh days of the experiment, the cellular viability, proliferation, and stemness were determined, using the MTT, trypan Blue, and flow cytometry assays in variable CNTs dosage.Results:In doses of 0.1 and 1 μg/ml, the expression of the surface markers were similar to the control groups on day three, but decreased in higher dosages on day seven. The viability of both groups was the same on day three, but in comparison to the control groups, was found to decrease in the higher dosages on day seven.Conclusion:The effect of CNTs on the viability and proliferation of ADSCs is a function of time and the doses used. Through further investigation by using these particles, we expect that we should be able to increase the viability and proliferation of ADSCs.